In the present time, the thin film transistor liquid crystal display (TFT-LCD) is developed to have high pixel per inch (ppi). One big obstacle for developing high ppi is the charging speed of the TFT. The production art for the TFT is to form a traditional metal oxide semiconductor layer structure. The mobility of electrons in the amorphous silicon is 0.5 to 1.0, and the mobility of electrons in the polysilicon is 30 to 300. Moreover, the production art is also a cause to decrease the mobility of the electrons. Therefore, designing a semiconductor layer structure and a TFT with reduced electric resistance to raise charging speed becomes an urgent problem.